Sharks have the remarkable ability to hunt prey even when not allowed to use sight or smell, based on a new research from the Mote Marine Laboratory, located in Sarasota, Florida.
Blacktip, nurse and bonnethead sharks had their senses tested by biologists who wanted to study the role senses played in hunting. Shark biologists humanely plugged the noses of sharks and covered their eyes in an effort to determine how the animals would hunt with reduced senses.
"The biggest motivation with this multisensory approach was to try to understand what they're really doing in a natural environment with sensory cues," Jayne Gardiner, a postdoctoral student at Mote who led the study, told Live Science.
For decades, marine biologists have wanted to test sharks by restricting one sense or another and recording hunting patterns. Doing this in the wild was nearly impossible, as the test subjects would swim away. Most aquariums don't have enough room to accurately record sharks as the carry out normal hunting patterns. Monte Marine Laboratory allowed researchers to watch sharks as far as 26 feet from their intended target.
Sharks were introduced to a pool containing favorite prey animals. A control experiment was run first, in which the sharks were allowed the use of all of their senses. In the next rounds of trials, the animals had one sense temporarily blocked.
Senses include "hydrodynamic imaging, electroreception, and touch... for orienting to, striking at, and capturing the prey. Experimental deprivation of senses showed how sharks exploit the many signals that comprise their sensory world, each sense coming into play as they provide more accurate information" about the prey, researchers wrote in the article announcing their findings.
Shark eyes were covered with plastic blindfolds in some trials, while their noses were blocked with cotton balls soaked in petroleum jelly in other runs. The predatory animals also use fine hairs on their skin to sense the flow of water in order to hunt. These hairs were temporarily removed using an antibiotic. Electrosensory senses were dampened by fitting the animals with an insulating material.
For sharks denied the use of the eyesight, smell became the first sense they used to track prey. As the predators drew closer to a potential meal, other senses assisted the animal in the hunt. Sharks were found to be much more adaptable to the loss of a single sense than most biologists had believed.
"Understanding how sharks sense and interact with their environment is vital for sustaining populations of these marine predators, which support the health of oceans around the world," researchers wrote in the press release announcing the findings.
Study of the senses of sharks is profiled the online journal Plos One.